I always set it to the highest tension possible. Sometimes, if after setting the tension I feel it not tensioned enough, I will release the tension, push down on the upper arm. If there is any slack or bow in the blade I will release the bottom blade clamp while still pushing down on the upper arm to release the slack or bow and then tighten the blade clamp, then re tension.
I never break blades because of high tension, but break blades because of low tension.